1. Field of the Invention
The present invention relates to a method of manufacturing a nozzle plate, a method of manufacturing a liquid ejection head including the nozzle plate, and a matrix structure for manufacturing the nozzle plate, and more particularly to a method of manufacturing a nozzle plate by plating, a method of manufacturing a liquid ejection head including the nozzle plate, and a matrix structure for manufacturing the nozzle plate.
2. Description of the Related Art
Methods are known for manufacturing a nozzle plate having a plurality of nozzle openings by plating. In general, a resist is patterned onto a substrate, and plating is carried out with this patterned resist (resist pattern).
Plating is generally carried out by electroforming (electroplating) which precipitates metal in a plating solution by means of externally applied electrical energy, or electroless plating which precipitates metal in a plating solution by means of a chemical reaction. The growth of the metal film is controlled by means of the current, in the case of electroforming, or by means of time in the case of electroless plating.
Japanese Patent Application Publication No. 8-132625 (and in particular, FIG. 1) discloses patterning of a resist and electroforming which is divided into two stages. More specifically, restrictor sections (nozzle apertures) are formed by electroforming with the first stage resist pattern, and flow channel sections (straight sections) connected to these restrictor sections are formed by electroforming with the second stage resist pattern.
Japanese Patent Application Publication No. 10-16236 (and in particular, FIGS. 4 to 11) discloses a method of manufacturing a nozzle plate (head base) having nozzle holes which each include cylindrically-shaped parallel sections and funnel-shaped curved sections into which ink is introduced. If the overall thickness of the nozzle plate is 100 μm, for example, then the length of the cylindrically-shaped parallel sections, which determine the size of the liquid droplets, is sufficiently small (10 μm to 15 μm). More specifically, the resist layer corresponding to the cylindrically-shaped parallel sections, which govern the ejection characteristics, is thin. After patterning this thin resist, electroforming is carried out, and the nozzle plate is thereby formed.
If the number of nozzles formed in the nozzle plate is increased in order to raise the speed of image forming, then the surface area of the nozzle plate increases, accordingly. On the other hand, in order to achieve high image quality, a high level of precision is required in the length of the nozzle holes (nozzle length) which governs the ejection characteristics.
If the nozzle plate is formed by electroforming, the growth of the metal film is generally controlled by the amount of current; however, there is a problem in that the nozzle plate formed by electroforming has poor uniformity in terms of the plate thickness. Hence, the length of the nozzles is uneven over the nozzle plate.
More specifically, as shown in FIG. 21, when electroforming is carried out with a patterned resist 71 on a substrate 70, there are variations in the growth of the metal film which forms a nozzle plate 501 on the substrate 70. In particular, if carrying out plating over a large surface area, it is difficult to maintain uniform growth of the metal film all over the substrate by controlling the amount of current.
In other words, when forming the nozzle plate 501 having the plurality of nozzle holes, it is difficult to maintain the precision of the nozzle length, and unevenness in the ejection amount may occur due to the unevenness in the nozzle length, thus leading to deterioration of image quality.
Since variations may occur in the nozzle length in this fashion, a step of polishing the nozzle plate is then necessary to achieve a uniform nozzle length, after the electroforming. However, if the polishing is carried out, there is a problem in that the shape of the edge sections of the nozzle holes is degraded, and eventually, the image quality deteriorates.
In the method disclosed in Japanese Patent Application Publication No. 8-132625, in both the restrictor sections (nozzle apertures) in the first stage and the flow channel sections (straight sections) in the second stage, the length is generally controlled by means of the amount of current in the electroforming process, and therefore uniformity over the nozzle plate is poor.
In Japanese Patent Application Publication No. 10-16236 also, compared to the overall thickness of the nozzle plate, the length of the cylindrical sections of the nozzle holes which governs the ejection characteristics is still generally controlled by the amount of current during the electroforming, regardless of the size of this length, and ultimately variations occur over the nozzle plate. Moreover, since the resist patterning of the first stage and the resist patterning of the second stage are separate steps, then it is difficult to align the positions of the two resist patterns. In other words, there is a problem in that the nozzle shapes lose axial symmetry. In general, a positional displacement of several micrometers or so may occur.
Furthermore, even in a case where a nozzle plate is manufactured by electroless plating, similar problems to those in a case of manufacturing by electroforming occur.